1
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Perea-Causin R, Brem S, Buchner F, Lu Y, Watanabe K, Taniguchi T, Lupton JM, Lin KQ, Malic E. Electrically tunable layer-hybridized trions in doped WSe 2 bilayers. Nat Commun 2024; 15:6713. [PMID: 39112462 PMCID: PMC11306803 DOI: 10.1038/s41467-024-50834-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2024] [Accepted: 07/16/2024] [Indexed: 08/10/2024] Open
Abstract
Doped van der Waals heterostructures host layer-hybridized trions, i.e. charged excitons with layer-delocalized constituents holding promise for highly controllable optoelectronics. Combining a microscopic theory with photoluminescence (PL) experiments, we demonstrate the electrical tunability of the trion energy landscape in naturally stacked WSe2 bilayers. We show that an out-of-plane electric field modifies the energetic ordering of the lowest lying trion states, which consist of layer-hybridized Λ -point electrons and layer-localized K-point holes. At small fields, intralayer-like trions yield distinct PL signatures in opposite doping regimes characterized by weak Stark shifts in both cases. Above a doping-asymmetric critical field, interlayer-like species are energetically favored and produce PL peaks with a pronounced Stark red-shift and a counter-intuitively large intensity arising from efficient phonon-assisted recombination. Our work presents an important step forward in the microscopic understanding of layer-hybridized trions in van der Waals heterostructures and paves the way towards optoelectronic applications based on electrically controllable atomically-thin semiconductors.
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Affiliation(s)
- Raul Perea-Causin
- Department of Physics, Chalmers University of Technology, Gothenburg, Sweden.
- Department of Physics, Stockholm University, Stockholm, Sweden.
| | - Samuel Brem
- Department of Physics, Philipps-Universität Marburg, Marburg, Germany
| | - Fabian Buchner
- Department of Physics, University of Regensburg, Regensburg, Germany
| | - Yao Lu
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, China
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, Tsukuba, Japan
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan
| | - John M Lupton
- Department of Physics, University of Regensburg, Regensburg, Germany
| | - Kai-Qiang Lin
- Department of Physics, University of Regensburg, Regensburg, Germany.
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, China.
| | - Ermin Malic
- Department of Physics, Philipps-Universität Marburg, Marburg, Germany.
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2
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Ju Q, Cai Q, Jian C, Hong W, Sun F, Wang B, Liu W. Infrared Interlayer Excitons in Twist-Free MoTe 2/MoS 2 Heterobilayers. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024:e2404371. [PMID: 39007276 DOI: 10.1002/adma.202404371] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2024] [Revised: 06/13/2024] [Indexed: 07/16/2024]
Abstract
Excitonic devices based on interlayer excitons in van der Waals heterobilayers are a promising platform for advancing photoelectric interconnection telecommunications. However, the absence of exciton emission in the crucial telecom C-band has constrained their practical applications. Here, this limitation is addressed by reporting exciton emission at 0.8 eV (1550 nm) in a chemically vapor-deposited, strictly aligned MoTe2/MoS2 heterobilayer, resulting from the direct bandgap transitions of interlayer excitons as identified by momentum-space imaging of their electrons and holes. The decay mechanisms dominated by direct radiative recombination ensure constant emission quantum yields, a basic demand for efficient excitonic devices. The atomically sharp interface enables the resolution of two narrowly-splitter transitions induced by spin-orbit coupling, further distinguished through the distinct Landé g-factors as the fingerprint of spin configurations. By electrical control, the double transitions coupling into opposite circularly-polarized photon modes, preserve or reverse the helicities of the incident light with a degree of polarization up to 90%. The Stark effect tuning extends the emission energy range by over 150 meV (270 nm), covering the telecom C-band. The findings provide a material platform for studying the excitonic complexes and significantly boost the application prospects of excitonic devices in silicon photonics and all-optical telecommunications.
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Affiliation(s)
- Qiankun Ju
- CAS Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Provincial Key Laboratory of Materials and Techniques toward Hydrogen Energy, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, P. R. China
- University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Qian Cai
- CAS Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Provincial Key Laboratory of Materials and Techniques toward Hydrogen Energy, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, P. R. China
| | - Chuanyong Jian
- CAS Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Provincial Key Laboratory of Materials and Techniques toward Hydrogen Energy, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, P. R. China
| | - Wenting Hong
- CAS Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Provincial Key Laboratory of Materials and Techniques toward Hydrogen Energy, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, P. R. China
| | - Fapeng Sun
- CAS Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Provincial Key Laboratory of Materials and Techniques toward Hydrogen Energy, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, P. R. China
- University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Bicheng Wang
- CAS Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Provincial Key Laboratory of Materials and Techniques toward Hydrogen Energy, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, P. R. China
| | - Wei Liu
- CAS Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Provincial Key Laboratory of Materials and Techniques toward Hydrogen Energy, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, P. R. China
- Fujian Science & Technology Innovation Laboratory for Optoelectronic Information of China, Fuzhou, Fujian, 350108, P. R. China
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3
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Hader J, Moloney JV. Photo Luminescence and Radiative Carrier Losses in Monolayer Transition Metal Dichalcogenides. NANO LETTERS 2024; 24:5231-5237. [PMID: 38639404 DOI: 10.1021/acs.nanolett.4c00705] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/20/2024]
Abstract
The carrier losses due to radiative recombination in monolayer transition metal dichalcogenides are studied using fully microscopic many-body models. The density- and temperature-dependent losses in various Mo- and W-based materials are shown to be dominated by Coulomb correlations beyond the Hartree-Fock level. Despite the much stronger Coulomb interaction in 2D materials, the radiative losses are comparable-if not weaker-than in conventional III-V materials. A strong dependence on the dielectric environment is found in agreement with experimental results.
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Affiliation(s)
- Jörg Hader
- Wyant College of Optical Sciences, University of Arizona, 1630 E. University Boulevard, Tucson, Arizona 85721, United States
- Nonlinear Control Strategies Inc., 7562 N. Palm Circle, Tucson, Arizona 85704, United States
| | - Jerome V Moloney
- Wyant College of Optical Sciences, University of Arizona, 1630 E. University Boulevard, Tucson, Arizona 85721, United States
- Nonlinear Control Strategies Inc., 7562 N. Palm Circle, Tucson, Arizona 85704, United States
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4
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Knorr W, Brem S, Meneghini G, Malic E. Polaron-induced changes in moiré exciton propagation in twisted van der Waals heterostructures. NANOSCALE 2024. [PMID: 38623653 DOI: 10.1039/d4nr00136b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/17/2024]
Abstract
Twisted transition metal dichalcogenides (TMDs) present an intriguing platform for exploring excitons and their transport properties. By introducing a twist angle, a moiré superlattice forms, providing a spatially dependent exciton energy landscape. Based on a microscopic many-particle theory, we investigate in this work polaron-induced changes in exciton transport properties in the exemplary MoSe2/WSe2 heterostructure. We demonstrate that polaron formation and the associated enhancement of the moiré exciton mass lead to a significant band flattening. As a result, the moiré inter-cell tunneling and the propagation velocity undergo noticeable temperature and twist-angle dependent changes. We predict a reduction of the hopping strength ranging from 80% at a twist angle of 1° to 30% at 3° at room temperature. The provided microscopic insights into the spatio-temporal exciton dynamics in presence of a moiré potential further expand the possibilities to tune charge and energy transport in 2D materials.
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Affiliation(s)
- Willy Knorr
- Department of Physics, Philipps University, 35037 Marburg, Germany.
| | - Samuel Brem
- Department of Physics, Philipps University, 35037 Marburg, Germany.
| | | | - Ermin Malic
- Department of Physics, Philipps University, 35037 Marburg, Germany.
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5
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Bennecke W, Windischbacher A, Schmitt D, Bange JP, Hemm R, Kern CS, D'Avino G, Blase X, Steil D, Steil S, Aeschlimann M, Stadtmüller B, Reutzel M, Puschnig P, Jansen GSM, Mathias S. Disentangling the multiorbital contributions of excitons by photoemission exciton tomography. Nat Commun 2024; 15:1804. [PMID: 38413573 PMCID: PMC10899218 DOI: 10.1038/s41467-024-45973-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2023] [Accepted: 02/08/2024] [Indexed: 02/29/2024] Open
Abstract
Excitons are realizations of a correlated many-particle wave function, specifically consisting of electrons and holes in an entangled state. Excitons occur widely in semiconductors and are dominant excitations in semiconducting organic and low-dimensional quantum materials. To efficiently harness the strong optical response and high tuneability of excitons in optoelectronics and in energy-transformation processes, access to the full wavefunction of the entangled state is critical, but has so far not been feasible. Here, we show how time-resolved photoemission momentum microscopy can be used to gain access to the entangled wavefunction and to unravel the exciton's multiorbital electron and hole contributions. For the prototypical organic semiconductor buckminsterfullerene (C60), we exemplify the capabilities of exciton tomography and achieve unprecedented access to key properties of the entangled exciton state including localization, charge-transfer character, and ultrafast exciton formation and relaxation dynamics.
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Affiliation(s)
- Wiebke Bennecke
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany
| | - Andreas Windischbacher
- Institute of Physics, University of Graz, NAWI Graz, Universitätsplatz 5, 8010, Graz, Austria
| | - David Schmitt
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany
| | - Jan Philipp Bange
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany
| | - Ralf Hemm
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern-Landau, Erwin-Schrödinger-Straße 46, 67663, Kaiserslautern, Germany
| | - Christian S Kern
- Institute of Physics, University of Graz, NAWI Graz, Universitätsplatz 5, 8010, Graz, Austria
| | - Gabriele D'Avino
- Univ. Grenoble Alpes, CNRS, Inst NEEL, F-38042, Grenoble, France
| | - Xavier Blase
- Univ. Grenoble Alpes, CNRS, Inst NEEL, F-38042, Grenoble, France
| | - Daniel Steil
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany
| | - Sabine Steil
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany
| | - Martin Aeschlimann
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern-Landau, Erwin-Schrödinger-Straße 46, 67663, Kaiserslautern, Germany
| | - Benjamin Stadtmüller
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern-Landau, Erwin-Schrödinger-Straße 46, 67663, Kaiserslautern, Germany
| | - Marcel Reutzel
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany
| | - Peter Puschnig
- Institute of Physics, University of Graz, NAWI Graz, Universitätsplatz 5, 8010, Graz, Austria
| | - G S Matthijs Jansen
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany.
| | - Stefan Mathias
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany.
- International Center for Advanced Studies of Energy Conversion (ICASEC), University of Göttingen, Göttingen, Germany.
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6
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Bange JP, Schmitt D, Bennecke W, Meneghini G, AlMutairi A, Watanabe K, Taniguchi T, Steil D, Steil S, Weitz RT, Jansen GSM, Hofmann S, Brem S, Malic E, Reutzel M, Mathias S. Probing electron-hole Coulomb correlations in the exciton landscape of a twisted semiconductor heterostructure. SCIENCE ADVANCES 2024; 10:eadi1323. [PMID: 38324690 PMCID: PMC10849592 DOI: 10.1126/sciadv.adi1323] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Accepted: 01/10/2024] [Indexed: 02/09/2024]
Abstract
In two-dimensional semiconductors, cooperative and correlated interactions determine the material's excitonic properties and can even lead to the creation of correlated states of matter. Here, we study the fundamental two-particle correlated exciton state formed by the Coulomb interaction between single-particle holes and electrons. We find that the ultrafast transfer of an exciton's hole across a type II band-aligned semiconductor heterostructure leads to an unexpected sub-200-femtosecond upshift of the single-particle energy of the electron being photoemitted from the two-particle exciton state. While energy relaxation usually leads to an energetic downshift of the spectroscopic signature, we show that this upshift is a clear fingerprint of the correlated interaction of the electron and hole parts of the exciton. In this way, time-resolved photoelectron spectroscopy is straightforwardly established as a powerful method to access electron-hole correlations and cooperative behavior in quantum materials. Our work highlights this capability and motivates the future study of optically inaccessible correlated excitonic and electronic states of matter.
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Affiliation(s)
- Jan Philipp Bange
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - David Schmitt
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Wiebke Bennecke
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Giuseppe Meneghini
- Fachbereich Physik, Philipps-Universität Marburg, 35032 Marburg, Germany
| | | | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Daniel Steil
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Sabine Steil
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - R. Thomas Weitz
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
- International Center for Advanced Studies of Energy Conversion (ICASEC), University of Göttingen, Göttingen, Germany
| | - G. S. Matthijs Jansen
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Stephan Hofmann
- Department of Engineering, University of Cambridge, Cambridge CB3 0FA, UK
| | - Samuel Brem
- Fachbereich Physik, Philipps-Universität Marburg, 35032 Marburg, Germany
| | - Ermin Malic
- Fachbereich Physik, Philipps-Universität Marburg, 35032 Marburg, Germany
- Department of Physics, Chalmers University of Technology, Gothenburg, Sweden
| | - Marcel Reutzel
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Stefan Mathias
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
- International Center for Advanced Studies of Energy Conversion (ICASEC), University of Göttingen, Göttingen, Germany
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7
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Xu C, Barden N, Alexeev EM, Wang X, Long R, Cadore AR, Paradisanos I, Ott AK, Soavi G, Tongay S, Cerullo G, Ferrari AC, Prezhdo OV, Loh ZH. Ultrafast Charge Transfer and Recombination Dynamics in Monolayer-Multilayer WSe 2 Junctions Revealed by Time-Resolved Photoemission Electron Microscopy. ACS NANO 2024; 18:1931-1947. [PMID: 38197410 DOI: 10.1021/acsnano.3c06473] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2024]
Abstract
The ultrafast carrier dynamics of junctions between two chemically identical, but electronically distinct, transition metal dichalcogenides (TMDs) remains largely unknown. Here, we employ time-resolved photoemission electron microscopy (TR-PEEM) to probe the ultrafast carrier dynamics of a monolayer-to-multilayer (1L-ML) WSe2 junction. The TR-PEEM signals recorded for the individual components of the junction reveal the sub-ps carrier cooling dynamics of 1L- and 7L-WSe2, as well as few-ps exciton-exciton annihilation occurring on 1L-WSe2. We observe ultrafast interfacial hole (h) transfer from 1L- to 7L-WSe2 on an ∼0.2 ps time scale. The resultant excess h density in 7L-WSe2 decays by carrier recombination across the junction interface on an ∼100 ps time scale. Reminiscent of the behavior at a depletion region, the TR-PEEM image reveals the h density accumulation on the 7L-WSe2 interface, with a decay length ∼0.60 ± 0.17 μm. These charge transfer and recombination dynamics are in agreement with ab initio quantum dynamics. The computed orbital densities reveal that charge transfer occurs from the basal plane, which extends over both 1L and ML regions, to the upper plane localized on the ML region. This mode of charge transfer is distinctive to chemically homogeneous junctions of layered materials and constitutes an additional carrier deactivation pathway that should be considered in studies of 1L-TMDs found alongside their ML, a common occurrence in exfoliated samples.
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Affiliation(s)
- Ce Xu
- School of Chemistry, Chemical Engineering and Biotechnology, and School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Natalie Barden
- School of Chemistry, Chemical Engineering and Biotechnology, and School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Evgeny M Alexeev
- Cambridge Graphene Centre, University of Cambridge, Cambridge CB3 0FA, U.K
| | - Xiaoli Wang
- College of Chemistry, Key Laboratory of Theoretical and Computational Photochemistry, Beijing Normal University, Beijing 100875, People's Republic of China
| | - Run Long
- College of Chemistry, Key Laboratory of Theoretical and Computational Photochemistry, Beijing Normal University, Beijing 100875, People's Republic of China
| | - Alisson R Cadore
- Cambridge Graphene Centre, University of Cambridge, Cambridge CB3 0FA, U.K
| | | | - Anna K Ott
- Cambridge Graphene Centre, University of Cambridge, Cambridge CB3 0FA, U.K
| | - Giancarlo Soavi
- Cambridge Graphene Centre, University of Cambridge, Cambridge CB3 0FA, U.K
- Institute of Solid State Physics, Friedrich Schiller University Jena, Max-Wien-Platz 1, 07743 Jena, Germany
| | - Sefaattin Tongay
- School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, Arizona 85287, United States
| | - Giulio Cerullo
- Department of Physics, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy
- IFN-CNR, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy
| | - Andrea C Ferrari
- Cambridge Graphene Centre, University of Cambridge, Cambridge CB3 0FA, U.K
| | - Oleg V Prezhdo
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Zhi-Heng Loh
- School of Chemistry, Chemical Engineering and Biotechnology, and School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
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8
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Perea-Causin R, Brem S, Schmidt O, Malic E. Trion Photoluminescence and Trion Stability in Atomically Thin Semiconductors. PHYSICAL REVIEW LETTERS 2024; 132:036903. [PMID: 38307073 DOI: 10.1103/physrevlett.132.036903] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Accepted: 12/04/2023] [Indexed: 02/04/2024]
Abstract
The optical response of doped monolayer semiconductors is governed by trions, i.e. photoexcited electron-hole pairs bound to doping charges. While their photoluminescence (PL) signatures have been identified in experiments, a microscopic model consistently capturing bright and dark trion peaks is still lacking. In this work, we derive a generalized trion PL formula on a quantum-mechanical footing, considering direct and phonon-assisted recombination mechanisms. We show the trion energy landscape in WSe_{2} by solving the trion Schrödinger equation. We reveal that the mass imbalance between equal charges results in less stable trions exhibiting a small binding energy and, interestingly, a large energetic offset from exciton peaks in PL spectra. Furthermore, we compute the temperature-dependent PL spectra for n- and p-doped monolayers and predict yet unobserved signatures originating from trions with an electron at the Λ point. Our work presents an important step toward a microscopic understanding of the internal structure of trions determining their stability and optical fingerprint.
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Affiliation(s)
- Raul Perea-Causin
- Department of Physics, Chalmers University of Technology, 412 96 Gothenburg, Sweden
| | - Samuel Brem
- Department of Physics, Philipps-Universität Marburg, 35032 Marburg, Germany
| | - Ole Schmidt
- Department of Physics, Philipps-Universität Marburg, 35032 Marburg, Germany
| | - Ermin Malic
- Department of Physics, Philipps-Universität Marburg, 35032 Marburg, Germany
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9
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Wang A, Jiang X, Zheng Q, Petek H, Zhao J. Ultrafast many-body bright-dark exciton transition in anatase TiO 2. Proc Natl Acad Sci U S A 2023; 120:e2307671120. [PMID: 37956295 PMCID: PMC10666115 DOI: 10.1073/pnas.2307671120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2023] [Accepted: 09/29/2023] [Indexed: 11/15/2023] Open
Abstract
The momentum-forbidden dark excitons can have a pivotal role in quantum information processing, Bose-Einstein condensation, and light-energy harvesting. Anatase TiO2 with an indirect band gap is a prototypical platform to study bright to momentum-forbidden dark exciton transition. Here, we examine, by GW plus the real-time Bethe-Salpeter equation combined with the nonadiabatic molecular dynamics (GW + rtBSE-NAMD), the many-body transition that occurs within 100 fs from the optically excited bright to the strongly bound momentum-forbidden dark excitons in anatase TiO2. Comparing with the single-particle picture in which the exciton transition is considered to occur through electron-phonon scattering, within the GW + rtBSE-NAMD framework, the many-body electron-hole Coulomb interaction activates additional exciton relaxation channels to notably accelerate the exciton transition in competition with other radiative and nonradiative processes. The existence of dark excitons and ultrafast bright-dark exciton transitions sheds insights into applications of anatase TiO2 in optoelectronic devices and light-energy harvesting as well as the formation process of dark excitons in semiconductors.
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Affiliation(s)
- Aolei Wang
- Department of Physics, University of Science and Technology of China, Hefei230026, China
| | - Xiang Jiang
- International Center for Quantum Design of Functional Materials/Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei230026, China
| | - Qijing Zheng
- Department of Physics, University of Science and Technology of China, Hefei230026, China
| | - Hrvoje Petek
- Department of Physics and Astronomy and the IQ Initiative, University of Pittsburgh, Pittsburgh, PA15260
| | - Jin Zhao
- Department of Physics, University of Science and Technology of China, Hefei230026, China
- International Center for Quantum Design of Functional Materials/Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei230026, China
- Department of Physics and Astronomy and the IQ Initiative, University of Pittsburgh, Pittsburgh, PA15260
- Hefei National Laboratory, University of Science and Technology of China, Hefei230088, China
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10
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Yagodkin D, Kumar A, Ankerhold E, Richter J, Watanabe K, Taniguchi T, Gahl C, Bolotin KI. Probing the Formation of Dark Interlayer Excitons via Ultrafast Photocurrent. NANO LETTERS 2023; 23:9212-9218. [PMID: 37788809 PMCID: PMC10603811 DOI: 10.1021/acs.nanolett.3c01708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Revised: 08/15/2023] [Indexed: 10/05/2023]
Abstract
Optically dark excitons determine a wide range of properties of photoexcited semiconductors yet are hard to access via conventional time-resolved spectroscopies. Here, we develop a time-resolved ultrafast photocurrent technique (trPC) to probe the formation dynamics of optically dark excitons. The nonlinear nature of the trPC makes it particularly sensitive to the formation of excitons occurring at the femtosecond time scale after the excitation. As a proof of principle, we extract the interlayer exciton formation time of 0.4 ps at 160 μJ/cm2 fluence in a MoS2/MoSe2 heterostructure and show that this time decreases with fluence. In addition, our approach provides access to the dynamics of carriers and their interlayer transport. Overall, our work establishes trPC as a technique to study dark excitons in various systems that are hard to probe by other approaches.
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Affiliation(s)
- Denis Yagodkin
- Department
of Physics, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany
| | - Abhijeet Kumar
- Department
of Physics, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany
| | - Elias Ankerhold
- Department
of Physics, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany
| | - Johanna Richter
- Department
of Physics, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany
| | - Kenji Watanabe
- Research
Center for Functional Materials, National
Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- International
Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Cornelius Gahl
- Department
of Physics, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany
| | - Kirill I. Bolotin
- Department
of Physics, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany
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11
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Li Y, Wan Q, Xu N. Recent Advances in Moiré Superlattice Systems by Angle-Resolved Photoemission Spectroscopy. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023:e2305175. [PMID: 37689836 DOI: 10.1002/adma.202305175] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Revised: 08/16/2023] [Indexed: 09/11/2023]
Abstract
The last decade has witnessed a flourish in 2D materials including graphene and transition metal dichalcogenides (TMDs) as atomic-scale Legos. Artificial moiré superlattices via stacking 2D materials with a twist angle and/or a lattice mismatch have recently become a fertile playground exhibiting a plethora of emergent properties beyond their building blocks. These rich quantum phenomena stem from their nontrivial electronic structures that are effectively tuned by the moiré periodicity. Modern angle-resolved photoemission spectroscopy (ARPES) can directly visualize electronic structures with decent momentum, energy, and spatial resolution, thus can provide enlightening insights into fundamental physics in moiré superlattice systems and guides for designing novel devices. In this review, first, a brief introduction is given on advanced ARPES techniques and basic ideas of band structures in a moiré superlattice system. Then ARPES research results of various moiré superlattice systems are highlighted, including graphene on substrates with small lattice mismatches, twisted graphene/TMD moiré systems, and high-order moiré superlattice systems. Finally, it discusses important questions that remain open, challenges in current experimental investigations, and presents an outlook on this field of research.
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Affiliation(s)
- Yiwei Li
- Institute for Advanced Studies (IAS), Wuhan University, Wuhan, 430072, China
| | - Qiang Wan
- Institute for Advanced Studies (IAS), Wuhan University, Wuhan, 430072, China
| | - Nan Xu
- Institute for Advanced Studies (IAS), Wuhan University, Wuhan, 430072, China
- Wuhan Institute of Quantum Technology, Wuhan, 430206, China
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12
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Dong S, Beaulieu S, Selig M, Rosenzweig P, Christiansen D, Pincelli T, Dendzik M, Ziegler JD, Maklar J, Xian RP, Neef A, Mohammed A, Schulz A, Stadler M, Jetter M, Michler P, Taniguchi T, Watanabe K, Takagi H, Starke U, Chernikov A, Wolf M, Nakamura H, Knorr A, Rettig L, Ernstorfer R. Observation of ultrafast interfacial Meitner-Auger energy transfer in a Van der Waals heterostructure. Nat Commun 2023; 14:5057. [PMID: 37598179 PMCID: PMC10439896 DOI: 10.1038/s41467-023-40815-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2023] [Accepted: 08/11/2023] [Indexed: 08/21/2023] Open
Abstract
Atomically thin layered van der Waals heterostructures feature exotic and emergent optoelectronic properties. With growing interest in these novel quantum materials, the microscopic understanding of fundamental interfacial coupling mechanisms is of capital importance. Here, using multidimensional photoemission spectroscopy, we provide a layer- and momentum-resolved view on ultrafast interlayer electron and energy transfer in a monolayer-WSe2/graphene heterostructure. Depending on the nature of the optically prepared state, we find the different dominating transfer mechanisms: while electron injection from graphene to WSe2 is observed after photoexcitation of quasi-free hot carriers in the graphene layer, we establish an interfacial Meitner-Auger energy transfer process following the excitation of excitons in WSe2. By analysing the time-energy-momentum distributions of excited-state carriers with a rate-equation model, we distinguish these two types of interfacial dynamics and identify the ultrafast conversion of excitons in WSe2 to valence band transitions in graphene. Microscopic calculations find interfacial dipole-monopole coupling underlying the Meitner-Auger energy transfer to dominate over conventional Förster- and Dexter-type interactions, in agreement with the experimental observations. The energy transfer mechanism revealed here might enable new hot-carrier-based device concepts with van der Waals heterostructures.
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Affiliation(s)
- Shuo Dong
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany.
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.
| | - Samuel Beaulieu
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany
- Université de Bordeaux - CNRS - CEA, CELIA, UMR5107, F33405, Talence, France
| | - Malte Selig
- Nichtlineare Optik und Quantenelektronik, Institut für Theoretische Physik, Technische Universität Berlin, 10623, Berlin, Germany
| | - Philipp Rosenzweig
- Max Planck Institute for Solid State Research, 70569, Stuttgart, Germany
| | - Dominik Christiansen
- Nichtlineare Optik und Quantenelektronik, Institut für Theoretische Physik, Technische Universität Berlin, 10623, Berlin, Germany
| | - Tommaso Pincelli
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany
| | - Maciej Dendzik
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany
- Department of Applied Physics, KTH Royal Institute of Technology, Hannes Alfvéns väg 12, 114 19, Stockholm, Sweden
| | - Jonas D Ziegler
- Institute of Applied Physics and Würzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062, Dresden, Germany
- Photonics Laboratory, ETH Zürich, 8093, Zürich, Switzerland
| | - Julian Maklar
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany
| | - R Patrick Xian
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany
- Department of Statistical Sciences, University of Toronto, 700 University Avenue, Toronto, ON, M5G 1Z5, Canada
| | - Alexander Neef
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany
| | - Avaise Mohammed
- Max Planck Institute for Solid State Research, 70569, Stuttgart, Germany
| | - Armin Schulz
- Max Planck Institute for Solid State Research, 70569, Stuttgart, Germany
| | - Mona Stadler
- Institute of Semiconductor Optics and Functional Interfaces, Research Center SCoPE and IQST, University of Stuttgart, 70569, Stuttgart, Germany
| | - Michael Jetter
- Institute of Semiconductor Optics and Functional Interfaces, Research Center SCoPE and IQST, University of Stuttgart, 70569, Stuttgart, Germany
| | - Peter Michler
- Institute of Semiconductor Optics and Functional Interfaces, Research Center SCoPE and IQST, University of Stuttgart, 70569, Stuttgart, Germany
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Hidenori Takagi
- Max Planck Institute for Solid State Research, 70569, Stuttgart, Germany
- Department of Physics, University of Tokyo, 113-0033, Tokyo, Japan
- Institute for Functional Matter and Quantum Technologies, University of Stuttgart, 70569, Stuttgart, Germany
| | - Ulrich Starke
- Max Planck Institute for Solid State Research, 70569, Stuttgart, Germany
| | - Alexey Chernikov
- Institute of Applied Physics and Würzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062, Dresden, Germany
| | - Martin Wolf
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany
| | - Hiro Nakamura
- Max Planck Institute for Solid State Research, 70569, Stuttgart, Germany
- Department of Physics, University of Arkansas, Fayetteville, AR, 72701, USA
| | - Andreas Knorr
- Nichtlineare Optik und Quantenelektronik, Institut für Theoretische Physik, Technische Universität Berlin, 10623, Berlin, Germany
| | - Laurenz Rettig
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany.
| | - Ralph Ernstorfer
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany.
- Institut für Optik und Atomare Physik, Technische Universität Berlin, 10623, Berlin, Germany.
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13
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Wei X, Liu C, Qin H, Ye Z, Liu X, Zong B, Li Z, Mao S. Fast, specific, and ultrasensitive antibiotic residue detection by monolayer WS 2-based field-effect transistor sensor. JOURNAL OF HAZARDOUS MATERIALS 2023; 443:130299. [PMID: 36356526 DOI: 10.1016/j.jhazmat.2022.130299] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2022] [Revised: 10/16/2022] [Accepted: 10/30/2022] [Indexed: 06/16/2023]
Abstract
Antibiotic residues cause increasing concern in environmental ecology and public health, which needs efficient analysis strategy for monitoring and control. In this study, a fast, specific, and ultrasensitive sensor based on field-effect transistor (FET) has been proposed for the detection of ampicillin (AMP). The sensor involves monolayer tungsten disulfide (WS2) nanosheet as the sensing channel, single-stranded DNA (ssDNA) as the sensing probe, and gold nanoparticle (Au NP) as the linker. The WS2/Au/ssDNA FET sensor responds rapidly to AMP in a wide linear detection range (10-12-10-6 M) and has low limit of detection (0.556 pM), which meets the permissible standards of AMP in water and food. The sensing mechanism study suggests that the excellent sensor response results from the increased number of negative charges in the Debye length and the consequent accumulation of holes in WS2 channel after the addition of AMP. Moreover, satisfactory sensing performance was confirmed in real water samples, indicating the potential application of the proposed method in practical AMP detection. The reported FET sensing strategy provides new insights in antibiotic analysis for risk assessment and control.
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Affiliation(s)
- Xiaojie Wei
- College of Environmental Science and Engineering, Biomedical Multidisciplinary Innovation Research Institute, Shanghai East Hospital, State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, 1239 Siping Road, Shanghai 200092, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China
| | - Chengbin Liu
- Institute for Agri-food Standards and Testing Technology, Shanghai Academy of Agricultural Sciences, Shanghai 201403, China
| | - Hehe Qin
- College of Environmental Science and Engineering, Biomedical Multidisciplinary Innovation Research Institute, Shanghai East Hospital, State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, 1239 Siping Road, Shanghai 200092, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China
| | - Ziwei Ye
- College of Environmental Science and Engineering, Biomedical Multidisciplinary Innovation Research Institute, Shanghai East Hospital, State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, 1239 Siping Road, Shanghai 200092, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China
| | - Xinru Liu
- College of Environmental Science and Engineering, Biomedical Multidisciplinary Innovation Research Institute, Shanghai East Hospital, State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, 1239 Siping Road, Shanghai 200092, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China
| | - Boyang Zong
- College of Environmental Science and Engineering, Biomedical Multidisciplinary Innovation Research Institute, Shanghai East Hospital, State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, 1239 Siping Road, Shanghai 200092, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China
| | - Zhuo Li
- College of Environmental Science and Engineering, Biomedical Multidisciplinary Innovation Research Institute, Shanghai East Hospital, State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, 1239 Siping Road, Shanghai 200092, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China
| | - Shun Mao
- College of Environmental Science and Engineering, Biomedical Multidisciplinary Innovation Research Institute, Shanghai East Hospital, State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, 1239 Siping Road, Shanghai 200092, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China.
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14
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Kunin A, Chernov S, Bakalis J, Li Z, Cheng S, Withers ZH, White MG, Schönhense G, Du X, Kawakami RK, Allison TK. Momentum-Resolved Exciton Coupling and Valley Polarization Dynamics in Monolayer WS_{2}. PHYSICAL REVIEW LETTERS 2023; 130:046202. [PMID: 36763432 DOI: 10.1103/physrevlett.130.046202] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Accepted: 12/22/2022] [Indexed: 06/18/2023]
Abstract
Using time- and angle-resolved photoemission, we present momentum- and energy-resolved measurements of exciton coupling in monolayer WS_{2}. We observe strong intravalley coupling between the B_{1s} exciton and A_{n>1} states. Our measurements indicate that the dominant valley depolarization mechanism conserves the exciton binding energy and momentum. While this conservation is consistent with Coulomb exchange-driven valley depolarization, we do not observe a momentum or energy dependence to the depolarization rate as would be expected for the exchange-based mechanism.
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Affiliation(s)
- Alice Kunin
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794, USA
| | - Sergey Chernov
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794, USA
| | - Jin Bakalis
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794, USA
| | - Ziling Li
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
| | - Shuyu Cheng
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
| | - Zachary H Withers
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, USA
| | - Michael G White
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794, USA
- Chemistry Division, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Gerd Schönhense
- Johannes Gutenberg-Universität, Institut für Physik, D-55099 Mainz, Germany
| | - Xu Du
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, USA
| | - Roland K Kawakami
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
| | - Thomas K Allison
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794, USA
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, USA
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15
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Thompson JJP, Lumsargis V, Feierabend M, Zhao Q, Wang K, Dou L, Huang L, Malic E. Interlayer exciton landscape in WS 2/tetracene heterostructures. NANOSCALE 2023; 15:1730-1738. [PMID: 36594632 DOI: 10.1039/d2nr02055f] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
The vertical stacking of two-dimensional materials into heterostructures gives rise to a plethora of intriguing optoelectronic properties and presents an unprecedented potential for technological development. While much progress has been made combining different monolayers of transition metal dichalcogenides (TMDs), little is known about TMD-based heterostructures including organic layers of molecules. Here, we present a joint theory-experiment study on a TMD/tetracene heterostructure demonstrating clear signatures of spatially separated interlayer excitons in low temperature photoluminescence spectra. Here, the Coulomb-bound electrons and holes are localized either in the TMD or in the molecule layer, respectively. We reveal both in theory and experiment signatures of the entire intra- and interlayer exciton landscape in the photoluminescence spectra. In particular, we find both in theory and experiment a pronounced transfer of intensity from the intralayer TMD exciton to a series of energetically lower interlayer excitons with decreasing temperature. In addition, we find signatures of phonon-sidebands stemming from these interlayer exciton states. Our findings shed light on the microscopic nature of interlayer excitons in TMD/molecule heterostructures and could have important implications for technological applications of these materials.
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Affiliation(s)
- Joshua J P Thompson
- Department of Physics, Philipps-Universität Marburg, 35037 Marburg, Germany.
| | - Victoria Lumsargis
- Department of Chemistry, Purdue University, West Lafayette, Indiana, 47907, USA
| | - Maja Feierabend
- Department of Physics, Chalmers University of Technology, 412 96 Gothenburg, Sweden
| | - Quichen Zhao
- Department of Chemistry, Purdue University, West Lafayette, Indiana, 47907, USA
- State Key Laboratory of Superhard Materials, Jilin University, Changchun, Jilin, 130012, China
| | - Kang Wang
- Davidson School of Chemical Engineering, Purdue University, West Lafayette, Indiana, 47907, USA
| | - Letian Dou
- Davidson School of Chemical Engineering, Purdue University, West Lafayette, Indiana, 47907, USA
| | - Libai Huang
- Department of Chemistry, Purdue University, West Lafayette, Indiana, 47907, USA
| | - Ermin Malic
- Department of Physics, Philipps-Universität Marburg, 35037 Marburg, Germany.
- Department of Physics, Chalmers University of Technology, 412 96 Gothenburg, Sweden
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16
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Tiede DO, Saigal N, Ostovar H, Döring V, Lambers H, Wurstbauer U. Exciton Manifolds in Highly Ambipolar Doped WS 2. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:3255. [PMID: 36145043 PMCID: PMC9504948 DOI: 10.3390/nano12183255] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Revised: 09/09/2022] [Accepted: 09/13/2022] [Indexed: 06/16/2023]
Abstract
The disentanglement of single and many particle properties in 2D semiconductors and their dependencies on high carrier concentration is challenging to experimentally study by pure optical means. We establish an electrolyte gated WS2 monolayer field-effect structure capable of shifting the Fermi level from the valence into the conduction band that is suitable to optically trace exciton binding as well as the single-particle band gap energies in the weakly doped regime. Combined spectroscopic imaging ellipsometry and photoluminescence spectroscopies spanning large n- and p-type doping with charge carrier densities up to 1014 cm-2 enable to study screening phenomena and doping dependent evolution of the rich exciton manifold whose origin is controversially discussed in literature. We show that the two most prominent emission bands in photoluminescence experiments are due to the recombination of spin-forbidden and momentum-forbidden charge neutral excitons activated by phonons. The observed interband transitions are redshifted and drastically weakened under electron or hole doping. This field-effect platform is not only suitable for studying exciton manifold but is also suitable for combined optical and transport measurements on degenerately doped atomically thin quantum materials at cryogenic temperatures.
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Affiliation(s)
- David Otto Tiede
- Institute of Physics, University of Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany
- Center for Soft Nanoscience (SoN), University of Münster, Busso-Peus-Straße 10, 48149 Münster, Germany
| | - Nihit Saigal
- Institute of Physics, University of Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany
- Center for Soft Nanoscience (SoN), University of Münster, Busso-Peus-Straße 10, 48149 Münster, Germany
| | - Hossein Ostovar
- Institute of Physics, University of Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany
- Center for Soft Nanoscience (SoN), University of Münster, Busso-Peus-Straße 10, 48149 Münster, Germany
| | - Vera Döring
- Institute of Physics, University of Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany
- Center for Soft Nanoscience (SoN), University of Münster, Busso-Peus-Straße 10, 48149 Münster, Germany
| | - Hendrik Lambers
- Institute of Physics, University of Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany
- Center for Soft Nanoscience (SoN), University of Münster, Busso-Peus-Straße 10, 48149 Münster, Germany
| | - Ursula Wurstbauer
- Institute of Physics, University of Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany
- Center for Soft Nanoscience (SoN), University of Münster, Busso-Peus-Straße 10, 48149 Münster, Germany
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17
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Formation of moiré interlayer excitons in space and time. Nature 2022; 608:499-503. [PMID: 35978130 DOI: 10.1038/s41586-022-04977-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Accepted: 06/14/2022] [Indexed: 11/09/2022]
Abstract
Moiré superlattices in atomically thin van der Waals heterostructures hold great promise for extended control of electronic and valleytronic lifetimes1-7, the confinement of excitons in artificial moiré lattices8-13 and the formation of exotic quantum phases14-18. Such moiré-induced emergent phenomena are particularly strong for interlayer excitons, where the hole and the electron are localized in different layers of the heterostructure19,20. To exploit the full potential of correlated moiré and exciton physics, a thorough understanding of the ultrafast interlayer exciton formation process and the real-space wavefunction confinement is indispensable. Here we show that femtosecond photoemission momentum microscopy provides quantitative access to these key properties of the moiré interlayer excitons. First, we elucidate that interlayer excitons are dominantly formed through femtosecond exciton-phonon scattering and subsequent charge transfer at the interlayer-hybridized Σ valleys. Second, we show that interlayer excitons exhibit a momentum fingerprint that is a direct hallmark of the superlattice moiré modification. Third, we reconstruct the wavefunction distribution of the electronic part of the exciton and compare the size with the real-space moiré superlattice. Our work provides direct access to interlayer exciton formation dynamics in space and time and reveals opportunities to study correlated moiré and exciton physics for the future realization of exotic quantum phases of matter.
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18
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Karni O, Esin I, Dani KM. Through the Lens of a Momentum Microscope: Viewing Light-Induced Quantum Phenomena in 2D Materials. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022:e2204120. [PMID: 35817468 DOI: 10.1002/adma.202204120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 06/23/2022] [Indexed: 06/15/2023]
Abstract
Van der Waals (vdW) materials at their 2D limit are diverse, flexible, and unique laboratories to study fundamental quantum phenomena and their future applications. Their novel properties rely on their pronounced Coulomb interactions, variety of crystal symmetries and spin-physics, and the ease of incorporation of different vdW materials to form sophisticated heterostructures. In particular, the excited state properties of many 2D semiconductors and semi-metals are relevant for their technological applications, particularly those that can be induced by light. In this paper, the recent advances made in studying out-of-equilibrium, light-induced, phenomena in these materials are reviewed using powerful, surface-sensitive, time-resolved photoemission-based techniques, with a particular emphasis on the emerging multi-dimensional photoemission spectroscopy technique of time-resolved momentum microscopy. The advances this technique has enabled in studying the nature and dynamics of occupied excited states in these materials are discussed. Then, the future research directions opened by these scientific and instrumental advancements are projected for studying the physics of 2D materials and the opportunities to engineer their band-structure and band-topology by laser fields.
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Affiliation(s)
- Ouri Karni
- Department of Applied Physics, Stanford University, Stanford, CA, 94305, USA
- SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA
| | - Iliya Esin
- Department of Physics, California Institute of Technology, Pasadena, CA, 91125, USA
| | - Keshav M Dani
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, 904-0495, Japan
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19
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Düvel M, Merboldt M, Bange JP, Strauch H, Stellbrink M, Pierz K, Schumacher HW, Momeni D, Steil D, Jansen GSM, Steil S, Novko D, Mathias S, Reutzel M. Far-from-Equilibrium Electron-Phonon Interactions in Optically Excited Graphene. NANO LETTERS 2022; 22:4897-4904. [PMID: 35649249 DOI: 10.1021/acs.nanolett.2c01325] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Comprehending far-from-equilibrium many-body interactions is one of the major goals of current ultrafast condensed matter physics research. Here, a particularly interesting but barely understood situation occurs during a strong optical excitation, where the electron and phonon systems can be significantly perturbed and the quasiparticle distributions cannot be described with equilibrium functions. In this work, we use time- and angle-resolved photoelectron spectroscopy to study such far-from-equilibrium many-body interactions for the prototypical material graphene. In accordance with theoretical simulations, we find remarkable transient renormalizations of the quasiparticle self-energy caused by the photoinduced nonequilibrium conditions. These observations can be understood by ultrafast scatterings between nonequilibrium electrons and strongly coupled optical phonons, which signify the crucial role of ultrafast nonequilibrium dynamics on many-body interactions. Our results advance the understanding of many-body physics in extreme conditions, which is important for any endeavor to optically manipulate or create non-equilibrium states of matter.
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Affiliation(s)
- Marten Düvel
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Marco Merboldt
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Jan Philipp Bange
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Hannah Strauch
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Michael Stellbrink
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Klaus Pierz
- Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany
| | | | - Davood Momeni
- Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany
| | - Daniel Steil
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - G S Matthijs Jansen
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Sabine Steil
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Dino Novko
- Institute of Physics, HR-10000 Zagreb, Croatia
| | - Stefan Mathias
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
- International Center for Advanced Studies of Energy Conversion (ICASEC), University of Göttingen, 37077 Göttingen, Germany
| | - Marcel Reutzel
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
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20
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Siday T, Sandner F, Brem S, Zizlsperger M, Perea-Causin R, Schiegl F, Nerreter S, Plankl M, Merkl P, Mooshammer F, Huber MA, Malic E, Huber R. Ultrafast Nanoscopy of High-Density Exciton Phases in WSe 2. NANO LETTERS 2022; 22:2561-2568. [PMID: 35157466 DOI: 10.1021/acs.nanolett.1c04741] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The density-driven transition of an exciton gas into an electron-hole plasma remains a compelling question in condensed matter physics. In two-dimensional transition metal dichalcogenides, strongly bound excitons can undergo this phase change after transient injection of electron-hole pairs. Unfortunately, unavoidable nanoscale inhomogeneity in these materials has impeded quantitative investigation into this elusive transition. Here, we demonstrate how ultrafast polarization nanoscopy can capture the Mott transition through the density-dependent recombination dynamics of electron-hole pairs within a WSe2 homobilayer. For increasing carrier density, an initial monomolecular recombination of optically dark excitons transitions continuously into a bimolecular recombination of an unbound electron-hole plasma above 7 × 1012 cm-2. We resolve how the Mott transition modulates over nanometer length scales, directly evidencing the strong inhomogeneity in stacked monolayers. Our results demonstrate how ultrafast polarization nanoscopy could unveil the interplay of strong electronic correlations and interlayer coupling within a diverse range of stacked and twisted two-dimensional materials.
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Affiliation(s)
- Thomas Siday
- Department of Physics and Regensburg Center for Ultrafast Nanoscopy (RUN), University of Regensburg, 93040 Regensburg, Germany
| | - Fabian Sandner
- Department of Physics and Regensburg Center for Ultrafast Nanoscopy (RUN), University of Regensburg, 93040 Regensburg, Germany
| | - Samuel Brem
- Department of Physics, Philipps-Universität Marburg, 35032 Marburg, Germany
- Department of Physics, Chalmers University of Technology, 41296 Gothenburg, Sweden
| | - Martin Zizlsperger
- Department of Physics and Regensburg Center for Ultrafast Nanoscopy (RUN), University of Regensburg, 93040 Regensburg, Germany
| | - Raul Perea-Causin
- Department of Physics, Chalmers University of Technology, 41296 Gothenburg, Sweden
| | - Felix Schiegl
- Department of Physics and Regensburg Center for Ultrafast Nanoscopy (RUN), University of Regensburg, 93040 Regensburg, Germany
| | - Svenja Nerreter
- Department of Physics and Regensburg Center for Ultrafast Nanoscopy (RUN), University of Regensburg, 93040 Regensburg, Germany
| | - Markus Plankl
- Department of Physics and Regensburg Center for Ultrafast Nanoscopy (RUN), University of Regensburg, 93040 Regensburg, Germany
| | - Philipp Merkl
- Department of Physics and Regensburg Center for Ultrafast Nanoscopy (RUN), University of Regensburg, 93040 Regensburg, Germany
| | - Fabian Mooshammer
- Department of Physics and Regensburg Center for Ultrafast Nanoscopy (RUN), University of Regensburg, 93040 Regensburg, Germany
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Markus A Huber
- Department of Physics and Regensburg Center for Ultrafast Nanoscopy (RUN), University of Regensburg, 93040 Regensburg, Germany
| | - Ermin Malic
- Department of Physics, Philipps-Universität Marburg, 35032 Marburg, Germany
- Department of Physics, Chalmers University of Technology, 41296 Gothenburg, Sweden
| | - Rupert Huber
- Department of Physics and Regensburg Center for Ultrafast Nanoscopy (RUN), University of Regensburg, 93040 Regensburg, Germany
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21
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Karni O, Barré E, Pareek V, Georgaras JD, Man MKL, Sahoo C, Bacon DR, Zhu X, Ribeiro HB, O'Beirne AL, Hu J, Al-Mahboob A, Abdelrasoul MMM, Chan NS, Karmakar A, Winchester AJ, Kim B, Watanabe K, Taniguchi T, Barmak K, Madéo J, da Jornada FH, Heinz TF, Dani KM. Structure of the moiré exciton captured by imaging its electron and hole. Nature 2022; 603:247-252. [PMID: 35264760 DOI: 10.1038/s41586-021-04360-y] [Citation(s) in RCA: 27] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Accepted: 12/14/2021] [Indexed: 11/09/2022]
Abstract
Interlayer excitons (ILXs) - electron-hole pairs bound across two atomically thin layered semiconductors - have emerged as attractive platforms to study exciton condensation1-4, single-photon emission and other quantum information applications5-7. Yet, despite extensive optical spectroscopic investigations8-12, critical information about their size, valley configuration and the influence of the moiré potential remains unknown. Here, in a WSe2/MoS2 heterostructure, we captured images of the time-resolved and momentum-resolved distribution of both of the particles that bind to form the ILX: the electron and the hole. We thereby obtain a direct measurement of both the ILX diameter of around 5.2 nm, comparable with the moiré-unit-cell length of 6.1 nm, and the localization of its centre of mass. Surprisingly, this large ILX is found pinned to a region of only 1.8 nm diameter within the moiré cell, smaller than the size of the exciton itself. This high degree of localization of the ILX is backed by Bethe-Salpeter equation calculations and demonstrates that the ILX can be localized within small moiré unit cells. Unlike large moiré cells, these are uniform over large regions, allowing the formation of extended arrays of localized excitations for quantum technology.
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Affiliation(s)
- Ouri Karni
- Department of Applied Physics, Stanford University, Stanford, CA, USA.,SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Elyse Barré
- SLAC National Accelerator Laboratory, Menlo Park, CA, USA.,Department of Electrical Engineering, Stanford University, Stanford, CA, USA
| | - Vivek Pareek
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, Japan
| | - Johnathan D Georgaras
- Department of Materials Science and Engineering, Stanford University, Stanford, CA, USA
| | - Michael K L Man
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, Japan
| | - Chakradhar Sahoo
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, Japan.,Tata Institute of Fundamental Research, Hyderabad, Gopanpally, Serlingampalli, Telangana, India
| | - David R Bacon
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, Japan
| | - Xing Zhu
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, Japan
| | | | - Aidan L O'Beirne
- SLAC National Accelerator Laboratory, Menlo Park, CA, USA.,Department of Physics, Stanford University, Stanford, CA, USA
| | - Jenny Hu
- Department of Applied Physics, Stanford University, Stanford, CA, USA
| | - Abdullah Al-Mahboob
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, Japan
| | - Mohamed M M Abdelrasoul
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, Japan
| | - Nicholas S Chan
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, Japan
| | - Arka Karmakar
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, Japan
| | - Andrew J Winchester
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, Japan
| | - Bumho Kim
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan
| | - Katayun Barmak
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY, USA
| | - Julien Madéo
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, Japan
| | - Felipe H da Jornada
- Department of Materials Science and Engineering, Stanford University, Stanford, CA, USA
| | - Tony F Heinz
- Department of Applied Physics, Stanford University, Stanford, CA, USA.,SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Keshav M Dani
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, Japan.
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22
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Huang D, Choi J, Shih CK, Li X. Excitons in semiconductor moiré superlattices. NATURE NANOTECHNOLOGY 2022; 17:227-238. [PMID: 35288673 DOI: 10.1038/s41565-021-01068-y] [Citation(s) in RCA: 62] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Accepted: 12/06/2021] [Indexed: 06/14/2023]
Abstract
Semiconductor moiré superlattices represent a rapidly developing area of engineered photonic materials and a new platform to explore correlated electron states and quantum simulation. In this Review, we briefly introduce early experiments that identified new exciton resonances in transition metal dichalcogenide heterobilayers and discuss several topics including two types of transition metal dichalcogenide moiré superlattice, new optical selection rules, early evidence of moiré excitons, and how the resonant energy, dynamics and diffusion properties of moiré excitons can be controlled via the twist angle. To interpret optical spectra, it is important to measure the energy modulation within a moiré supercell. In this context, we describe a few scanning tunnelling microscopy experiments that measure the moiré potential landscape directly. Finally, we review a few recent experiments that applied excitonic optical spectroscopy to probe correlated electron phenomena in transition metal dichalcogenide moiré superlattices.
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Affiliation(s)
- Di Huang
- Physics Department and Center for Complex Quantum Systems, The University of Texas-Austin, Austin, TX, USA.
| | - Junho Choi
- Physics Department and Center for Complex Quantum Systems, The University of Texas-Austin, Austin, TX, USA
- Texas Materials Institute and Center for Dynamics and Control of Materials, The University of Texas-Austin, Austin, TX, USA
| | - Chih-Kang Shih
- Physics Department and Center for Complex Quantum Systems, The University of Texas-Austin, Austin, TX, USA
- Texas Materials Institute and Center for Dynamics and Control of Materials, The University of Texas-Austin, Austin, TX, USA
| | - Xiaoqin Li
- Physics Department and Center for Complex Quantum Systems, The University of Texas-Austin, Austin, TX, USA.
- Texas Materials Institute and Center for Dynamics and Control of Materials, The University of Texas-Austin, Austin, TX, USA.
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23
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Thompson JJP, Brem S, Fang H, Antón-Solanas C, Han B, Shan H, Dash SP, Wieczorek W, Schneider C, Malic E. Valley-exchange coupling probed by angle-resolved photoluminescence. NANOSCALE HORIZONS 2021; 7:77-84. [PMID: 34796891 DOI: 10.1039/d1nh00302j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The optical properties of monolayer transition metal dichalcogenides are dominated by tightly-bound excitons. They form at distinct valleys in reciprocal space, and can interact via the valley-exchange coupling, modifying their dispersion considerably. Here, we predict that angle-resolved photoluminescence can be used to probe the changes of the excitonic dispersion. The exchange-coupling leads to a unique angle dependence of the emission intensity for both circularly and linearly-polarised light. We show that these emission characteristics can be strongly tuned by an external magnetic field due to the valley-specific Zeeman-shift. We propose that angle-dependent photoluminescence measurements involving both circular and linear optical polarisation as well as magnetic fields should act as strong verification of the role of valley-exchange coupling on excitonic dispersion and its signatures in optical spectra.
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Affiliation(s)
- Joshua J P Thompson
- Department of Physics, Chalmers University of Technology, Gothenburg 412 96, Sweden.
| | - Samuel Brem
- Department of Physics, Philipps-Universität Marburg, Renthof 7, Marburg 35032, Germany
| | - Hanlin Fang
- Department of Microtechnology and Nanoscience (MC2), Chalmers University of Technology, Gothenburg 412 96, Sweden
| | | | - Bo Han
- Institute of Physics, University of Oldenburg, 26129 Oldenburg, Germany
| | - Hangyong Shan
- Institute of Physics, University of Oldenburg, 26129 Oldenburg, Germany
| | - Saroj P Dash
- Department of Microtechnology and Nanoscience (MC2), Chalmers University of Technology, Gothenburg 412 96, Sweden
| | - Witlef Wieczorek
- Department of Microtechnology and Nanoscience (MC2), Chalmers University of Technology, Gothenburg 412 96, Sweden
| | | | - Ermin Malic
- Department of Physics, Chalmers University of Technology, Gothenburg 412 96, Sweden.
- Department of Physics, Philipps-Universität Marburg, Renthof 7, Marburg 35032, Germany
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24
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Rosati R, Wagner K, Brem S, Perea-Causín R, Ziegler JD, Zipfel J, Taniguchi T, Watanabe K, Chernikov A, Malic E. Non-equilibrium diffusion of dark excitons in atomically thin semiconductors. NANOSCALE 2021; 13:19966-19972. [PMID: 34821228 DOI: 10.1039/d1nr06230a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Atomically thin semiconductors provide an excellent platform to study intriguing many-particle physics of tightly-bound excitons. In particular, the properties of tungsten-based transition metal dichalcogenides are determined by a complex manifold of bright and dark exciton states. While dark excitons are known to dominate the relaxation dynamics and low-temperature photoluminescence, their impact on the spatial propagation of excitons has remained elusive. In our joint theory-experiment study, we address this intriguing regime of dark state transport by resolving the spatio-temporal exciton dynamics in hBN-encapsulated WSe2 monolayers after resonant excitation. We find clear evidence of an unconventional, time-dependent diffusion during the first tens of picoseconds, exhibiting strong deviation from the steady-state propagation. Dark exciton states are initially populated by phonon emission from the bright states, resulting in creation of hot (unequilibrated) excitons whose rapid expansion leads to a transient increase of the diffusion coefficient by more than one order of magnitude. These findings are relevant for both fundamental understanding of the spatio-temporal exciton dynamics in atomically thin materials as well as their technological application by enabling rapid diffusion.
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Affiliation(s)
- Roberto Rosati
- Department of Physics, Philipps-Universität Marburg, Renthof 7, D-35032 Marburg, Germany.
| | - Koloman Wagner
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Würzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062 Dresden, Germany
| | - Samuel Brem
- Department of Physics, Philipps-Universität Marburg, Renthof 7, D-35032 Marburg, Germany.
| | - Raül Perea-Causín
- Chalmers University of Technology, Department of Physics, 412 96 Gothenburg, Sweden
| | - Jonas D Ziegler
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Würzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062 Dresden, Germany
| | - Jonas Zipfel
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Ibaraki 305-004, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Ibaraki 305-004, Japan
| | - Alexey Chernikov
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Würzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062 Dresden, Germany
| | - Ermin Malic
- Department of Physics, Philipps-Universität Marburg, Renthof 7, D-35032 Marburg, Germany.
- Chalmers University of Technology, Department of Physics, 412 96 Gothenburg, Sweden
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25
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Helmrich S, Sampson K, Huang D, Selig M, Hao K, Tran K, Achstein A, Young C, Knorr A, Malic E, Woggon U, Owschimikow N, Li X. Phonon-Assisted Intervalley Scattering Determines Ultrafast Exciton Dynamics in MoSe_{2} Bilayers. PHYSICAL REVIEW LETTERS 2021; 127:157403. [PMID: 34678033 DOI: 10.1103/physrevlett.127.157403] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2020] [Revised: 04/23/2021] [Accepted: 08/23/2021] [Indexed: 06/13/2023]
Abstract
While valleys (energy extrema) are present in all band structures of solids, their preeminent role in determining exciton resonances and dynamics in atomically thin transition metal dichalcogenides (TMDC) is unique. Using two-dimensional coherent electronic spectroscopy, we find that exciton decoherence occurs on a much faster timescale in MoSe_{2} bilayers than that in the monolayers. We further identify two population relaxation channels in the bilayer, a coherent and an incoherent one. Our microscopic model reveals that phonon-emission processes facilitate scattering events from the K valley to other lower-energy Γ and Λ valleys in the bilayer. Our combined experimental and theoretical studies unequivocally establish different microscopic mechanisms that determine exciton quantum dynamics in TMDC monolayers and bilayers. Understanding exciton quantum dynamics provides critical guidance to the manipulation of spin-valley degrees of freedom in TMDC bilayers.
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Affiliation(s)
- Sophia Helmrich
- Department of Optics and Atomic Physics, Technical University Berlin, Berlin 10623, Germany
| | - Kevin Sampson
- Department of Physics and Center for Complex Quantum Systems, The University of Texas at Austin, Austin, Texas 78712, USA
- Center for Dynamics and Control of Materials and Texas Materials Institute, 2501 Speedway, Austin, Texas 78712, USA
| | - Di Huang
- Department of Physics and Center for Complex Quantum Systems, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Malte Selig
- Nichtlineare Optik und Quantenelektronik, Institut für Theoretische Physik, Technische Universität Berlin, 10623 Berlin, Germany
| | - Kai Hao
- Department of Physics and Center for Complex Quantum Systems, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Kha Tran
- Department of Physics and Center for Complex Quantum Systems, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Alexander Achstein
- Department of Optics and Atomic Physics, Technical University Berlin, Berlin 10623, Germany
| | - Carter Young
- Department of Physics and Center for Complex Quantum Systems, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Andreas Knorr
- Nichtlineare Optik und Quantenelektronik, Institut für Theoretische Physik, Technische Universität Berlin, 10623 Berlin, Germany
| | - Ermin Malic
- Department of Physics, Philipps University Marburg, 35037 Marburg, Germany
| | - Ulrike Woggon
- Department of Optics and Atomic Physics, Technical University Berlin, Berlin 10623, Germany
| | - Nina Owschimikow
- Department of Optics and Atomic Physics, Technical University Berlin, Berlin 10623, Germany
| | - Xiaoqin Li
- Department of Physics and Center for Complex Quantum Systems, The University of Texas at Austin, Austin, Texas 78712, USA
- Center for Dynamics and Control of Materials and Texas Materials Institute, 2501 Speedway, Austin, Texas 78712, USA
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26
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Wagner K, Zipfel J, Rosati R, Wietek E, Ziegler JD, Brem S, Perea-Causín R, Taniguchi T, Watanabe K, Glazov MM, Malic E, Chernikov A. Nonclassical Exciton Diffusion in Monolayer WSe_{2}. PHYSICAL REVIEW LETTERS 2021; 127:076801. [PMID: 34459627 DOI: 10.1103/physrevlett.127.076801] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Accepted: 06/24/2021] [Indexed: 06/13/2023]
Abstract
We experimentally demonstrate time-resolved exciton propagation in a monolayer semiconductor at cryogenic temperatures. Monitoring phonon-assisted recombination of dark states, we find a highly unusual case of exciton diffusion. While at 5 K the diffusivity is intrinsically limited by acoustic phonon scattering, we observe a pronounced decrease of the diffusion coefficient with increasing temperature, far below the activation threshold of higher-energy phonon modes. This behavior corresponds neither to well-known regimes of semiclassical free-particle transport nor to the thermally activated hopping in systems with strong localization. Its origin is discussed in the framework of both microscopic numerical and semiphenomenological analytical models illustrating the observed characteristics of nonclassical propagation. Challenging the established description of mobile excitons in monolayer semiconductors, these results open up avenues to study quantum transport phenomena for excitonic quasiparticles in atomically thin van der Waals materials and their heterostructures.
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Affiliation(s)
- Koloman Wagner
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
| | - Jonas Zipfel
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Roberto Rosati
- Department of Physics, Philipps-Universität Marburg, Renthof 7, Marburg D-35032, Germany
| | - Edith Wietek
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
| | - Jonas D Ziegler
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
| | - Samuel Brem
- Department of Physics, Philipps-Universität Marburg, Renthof 7, Marburg D-35032, Germany
| | - Raül Perea-Causín
- Department of Physics, Chalmers University of Technology, Fysikgården 1, 41258 Gothenburg, Sweden
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Ibaraki 305-004, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Ibaraki 305-004, Japan
| | | | - Ermin Malic
- Department of Physics, Philipps-Universität Marburg, Renthof 7, Marburg D-35032, Germany
- Department of Physics, Chalmers University of Technology, Fysikgården 1, 41258 Gothenburg, Sweden
| | - Alexey Chernikov
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Würzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062 Dresden, Germany
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